One type of submersible well fluid pump has an electrical motor operatively connected with a centrifugal pump. The pump has a large number of stages, each stage having an impeller and a diffuser. A shaft rotated by the motor rotates the impellers relative to the diffusers. Each impeller has passages that lead upward and outward to the next upward diffuser. Each diffuser has diffuser passages that extend upward and inward to the next upward impeller.
The diffusers are stacked together in a housing of the pump. Typically, elastomeric o-ring seals extend around the outer wall of each diffuser and seal against the inner wall surface of the pump housing. Also, the stack of diffusers has an anti-rotation feature to prevent rotation of the diffusers in the housing.
During manufacturing, technicians assemble the impellers and diffusers on the shaft, then push the assembly into the housing. The o-ring seals slide against the inner wall surface of the pump housing during insertion. Providing a larger annular clearance between the outer walls of the diffusers and the inner wall surface of the pump housing facilitates inserting the assembly. However, the larger clearance may compromise the integrity of the o-ring seals.